Dry thinned starches, process for producing dry thinned starches, and products and compositions thereof

ABSTRACT

A novel dry thinned starch produced by continuously feeding a mixture of a base starch and a chemical which hydrolyses the glycosidic linkage of starch to a plug flow reactor, passing the mixture through the reactor, recovering the mixture and neutralizing the mixture. The present invention also includes starches produced by the process and paper products produced from the starch and coated with the starch.

BACKGROUND OF THE INVENTION

This invention relates to novel dry thinned starches, continuousprocesses for producing dry thinned starches and to compositions andproducts thereof. More particularly, the invention relates to drythinned starches produced in a continuous process under specifiedinterrelated process conditions. It also relates to compositionsincorporating such starches such as paper sizing and coatingcompositions and to paper products produced from such compositions.

SUMMARY OF THE INVENTION

The present invention produces novel dry thinned starch. The dry thinnedstarches are produced by continuously feeding a mixture of a base starchand a chemical which hydrolyses the glycosidic linkage of starch to aplug flow reactor, passing the mixture through the reactor, recoveringthe mixture and neutralizing the mixture.

The invention also includes starches produced by the process and paperproducts produced from the starch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram of a dry thinning process.

DETAILED DESCRIPTION

INTRODUCTION

Starches are widely used in paper coating formulations to give therequired rheology, water holding, and binding properties. Typically, lowviscosity starches are required to achieve high solids in the coatingsystem. High solids are needed to reduce the drying cost and to reducesurface deformation due to excessive shrinkage of the surface layerduring drying. Another requirement of such starches is that they exhibitresistance to retrograding, i.e., the formation of insolubleprecipitates from the association of poorly soluble linear dextrinspresent in starch solution and low DE (dextrose equivalent)hydrolyzates.

Hydroxyethylated dent corn starches are presently used in such coatingsbecause they are low cost and their cooked pastes resist retrogradationsubstantially better than unmodified dent corn starch. Thinnedunsubstituted waxy starches have the same or greater resistance toretrogradation than the hydroxyethylated dent starches and are lessexpensive to produce.

Low viscosity starches are prepared by reducing the molecular weight ofthe starch polymers. Most common processes use either an acid, anenzyme, or an oxidizing agent for molecular weight reduction. Thesethinning reactions are typically carried out in an aqueous slurry of thestarch. Upon thinning the starches to the preferred viscosity, itbecomes necessary to filter the starch from the slurry so that it can bedried and recovered. Some of the soluble starch and salts ofneutralization generated by the thinning reaction are substantially lostin the effluent. This results in a significant economic loss due toyield loss, drying inefficiencies and an increased load on the effluenttreatment facilities. In the case of hydroxyethylated starch, a portionof the hydroxyethyl substituent is also lost which increases theeconomic disadvantages of its use.

An alternate route for making starches with the above performancecharacteristics, but without the economic loss resulting from presentprocesses, has been found. The essential characteristics of this methodare the injection of a glycosidic hydrolyzing chemical into starch whichis in a non-slurry state, heating at a temperature and for a timenecessary to produce a starch with the required viscosity, and thenneutralization. No washing of the final product is required. Thisprocess can be used for any type of starch to be thinned.

Dry thinned waxy starch products allow higher solids concentrationcompositions that give the same viscosity as lower concentrationmodified starch compositions. In paper manufacture, this is an advantageat the sizepress and coater which are both viscosity constrained. Waxystarch is unique in this feature compared to modified or unmodified dentcorn starch.

A process has been developed for the continuous dry reaction of starch.This process is used for reduction of molecular weight (thinning) viachemical hydrolysis of the glycosidic linkages of starch. A preferredmeans of chemical hydrolysis is by gaseous acidification. A primary usefor these starches is in the paper industry. They will be used at thesize press and on paper coaters. Their purpose is to add viscosity (flowproperties) and water holding to the coating colors and strength to thesheet at the size press.

Any starch source including common dent corn, waxy maize, potato, waxymilo, arrowroot, wheat, rice, tapioca and sago starches can be thinnedby this process. The preferred base starches for paper applications arewaxy starches (amylopectins) derived from waxy maize due to theirresistance to retrogradation. Chemically modified dent starches (atleast 20% amylose) also exhibit resistance to retrogradation. Chemicalmodification contributes resistance to retrogradation via sterichindrance. Linear starch chains are prevented from aligning due to theaddition of substituents. Such starches include starches modified withepoxides such as ethylene oxide, propylene oxide and epichlorohydrin. Ofthese, starches modified with ethylene oxide are preferred in paperapplications. The source starch can be chemically modified by othermeans such as 1) bleaching with hydrogen peroxide, ammonium persulfate,chlorine, chlorite and permanganate; 2) oxidation with chlorine; 3)esterification with acetic anhydride, phosphates, octenyl succinicanhydride, phosphorous oxychloride, succinic anyhydride and vinylacetate; 4) etherification with acrolein or 5) formation of cationicderivatives with reagents such as 2,3-epoxypropyltrimethylammoniumchloride or (4-chlorobutene-2) trimethylammonium chloride prior to thedry thinning process. Such starches are well known in the art and arecommercially available. For example, ETHYLEX® gums are available from A.E. Staley Manufacturing Co. of Decatur, Ill., are derivatives of cornstarch in which hydroxyethyl groups have been attached to the starch.Although not as resistant to retrogradation, useful starch products canalso be prepared by the process of the invention from common dent cornstarch. The dry thinned modified starches produced by this process canbe used in food and textile applications in addition to the describedpaper applications. In such cases, the dry thinned modified starches areused to replace modified starches which have been thinned in traditionalaqueous slurry processes.

DRY THINNING PROCESS

A dry thinning process has been discovered wherein the molecular weightof base starches is reduced by the reaction of the starch with aglycosidic hydrolyzing chemical in a continuous reactor. Any chemicalwhich hydrolyses the glycosidic linkage of starch in the reactionconditions described can be used. There are three primary groups ofhydrolyzing chemicals that can be used. Group I includes acids such ashydrogen chloride gas (gaseous HCl), hydrochloric acid (HCl) andsulfuric acid; Group II includes oxidants such as ammonium persulfate,hydrogen peroxide and chlorine gas; and Group III includes acids such assulfur dioxide gas, carbon dioxide gas, nitric acid, phosphoric acid,monochloroacetic acid, ammonium chloride (Lewis acid) and calciumchloride (Lewis acid). Group I chemicals are preferred for use in thedry thinning reaction, with the most preferred hydrolysis chemical beinggaseous HCl. Pressurized reactors maybe required when sulfur dioxide andcarbon dioxide are used as the hydrolyzing chemicals. In some instancesit may be beneficial to use two or more hydrolyzing chemicals togetherin the process.

The following variables are critical to control the thinning rate:temperature, hydrolyzing chemical addition level, moisture level of theincoming starch, and residence time in the reactor. From these variablesthe final molecular weight of the starch and the amount of drysubstances starch required to give 1000 centipoise of viscosity at 35°C. in an RVA viscometer (VscGm DS) can be predicted. Typically this willbe from about 1.5 to about 13 grams starch, dry basis (GmDS starch). TheRVA viscometer is a computer controlled, electrically heated, watercooled, mixing and cooking device designed to measure viscosity ofmaterials cooked under different time/temperature profiles. The RVA unitutilizes a 28 gram sample compartment. When used to evaluate productsmade by this invention, it has been found that a 1.5 to 13 gram starchsample should be placed in the sample compartment. Sufficient water isadded to the sample compartment to reach 28.0 grams total weight. TheRVA is an instrument for measuring starch cooking properties thatprovides a practical means for identifying the end point of a thinningreaction. The Rapid Visco Analyzer is made in Australia and marketed inthe United States by Foss Food Technology of Eden Prairie, Minn. Thisinstrument allows for rapid generation of viscosity profiles. Standardoils with known viscosities are used to calibrate the RVA over aspecified temperature range. This calibration is used to convert RVAunits to centipoise.

Experimental design response surfaces can be generated which describethe relationship between the dependent variable (viscosity) and theindependent variables (temperature, hydrolyzing chemical level,retention time, initial moisture content). Such a relationship can bedefined by an equation of the form:

    Vsc Gm DS=a+bT+cC+dR-eM

wherein a, b, c, d and e are empirically derived constants that willvary with reactor design and configuration and T is temperature, C ischemical concentration (weight %), R is residence time in the reactorand M is the initial moisture content of the starch (loss on drying).

The starch products of the invention are prepared in a continuousreactor exhibiting plug flow. The advantages of plug flow reactorsversus reactors wherein mixing occurs is that the variables, mostnotably retention time, can be held substantially identical for all ofthe starch being processed whereas In mixed reactors the starch will besubjected to variable processing times.

Plug flow reactors are known in the art. Such reactors, also referred toas mass flow purge and conditioning vessels, and mass flow bins aredesigned to allow material in the reactor to flow uniformly from thereactor in a first in first out fashion with little or no mixing of thematerial. It is recognized that it is difficult, if not impossible, toachieve perfect plug flow in mass flow bins with dry flowable productssuch as starch. For purposes of this invention, it is the intent toapproach plug flow of the starch and hydrolyzing chemical in the massflow bin/reactor. Plug flow is meant to describe a process in whichsubstantially all of the starch flows through the reactor in a first infirst out fashion with little or no channeling of the material in themass flow bin/reactor.

To obtain substantially mass flow in such a vessel, the conical slope ofthe vessel should be about 65 to about 75 degrees. The vessel shouldhave a height to width ratio of at least 2 to 1.

Attainment of plug flow conditions can be determined by measuringcertain molecular weight parameters of the thinned product. Twomeasurements are made by using gel permeation chromatography (GPC) todetermine molecular weight parameters of the finished product. The firstvalue, Mw, is the average molecular weight of the thinned starchproduct, while the second value, Mn, is the number average molecularweight of the thinned starch product. In an ideal dry thinning processsuch as a batch process, the width of molecular weight distributiondecreases as the thinning reaction proceeds. The width of the molecularweight distribution is defined as the difference between Mw and Mn.Perfect plug flow conditions should mimic batch process results. Whenresults from the plug flow continuous process deviate substantially fromthe batch results, it would be an indication that channeling or non-plugflow conditions exist in the continuous process. The width of themolecular weight distribution can be expressed as (Mw-Mn)/1000. Plugflow conditions exist in the continuous process of this invention whenthe width of the molecular weight distribution of the thinned productwhen expressed as (Mw-Mn)/1000 is within + or -25% of the same value fora batch thinned product of the same viscosity.

The process of the instant invention is carried out on a base starchhaving a moisture content between about 5 percent and about 20 percentweight basis. Preferably the base starch will have a moisture content ofabout 5 percent to about 17 percent. The most preferred range is fromabout 10 percent to about 13 percent.

The base starch should be heated to a temperature of about 70° F. (21°C.) to about 170° F. (77° C.) before entering the reactor, and beforechemical addition. Preferably the base starch will be at a temperatureof about 100° F. (38° C.) to about 140° F. (60° C.).

Prior to entering into the reactor, the hydrolyzing chemical is injectedinto the starch as a gas or in a finely dispersed liquid. Group Ichemicals are injected in an amount from about 0.04 percent to about 0.5weight percent basis dry starch. Preferably the Group I hydrolyzingchemical will be present in the starch at a concentration of about 0.1to about 0.4 weight percent. When Group II and III hydrolyzing chemicalsare used as the thinning agents, higher amounts of the chemicals arerequired to obtain the desired thinning. Group II and III hydrolyzingchemicals will be present in the starch at a concentration of about 0.1to about 2.0 weight percent.

Injection of the hydrolyzing chemical into the starch base requiresspecial handling to avoid degradation and coloring of the starch andpotential process shut downs. When anhydrous HCl comes in contact withthe base starch, hydrochloric acid is formed from the reaction of theHCl and moisture in the starch. If sufficient quantities of hydrochloricacid form on the starch blackening can occur.

To prevent these problems, steps must be taken to insure equaldispersion of the hydrolysis chemical on the starch. This isaccomplished by injecting the hydrolyzing chemical into the air streamof the pneumatic conveying line transporting the base starch to thereactor before the starch is added to the line.

The starch-hydrolyzing chemical mixture is introduced into a reactorvessel adapted to provide a mass flow regime, i.e., thestarch-hydrolyzing chemical mixture flows through the reactor in a firstin and first out manner and without substantial mixing of the starch.Such a flow regime ensures that substantially all of thestarch-hydrolyzing chemical mixture experiences substantially the sameresidence time in the reactor.

While in the reactor, the starch-hydrolyzing chemical mixture ismaintained at a temperature of about 70° F. to about 170° F. Preferablythe temperature will be from about 100° F. to about 140° F.

The starch-hydrolyzing chemical mixture will be resident in the reactorfor a time of about 0.5 to about 6 hours. Preferably the resident timewill be from about 1 to about 4 hours.

Upon exiting the reactor the starch-hydrolyzing chemical mixture isneutralized. For example, when HCl or sulfuric acid is used as thehydrolyzing chemical, the thinned starch can be neutralized withanhydrous ammonia or with aqueous bases. Spraying an aqueous solution ofsoda ash (sodium carbonate) on the starch is the preferredneutralization technique as it provides better uniformity ofneutralization and provides a convenient method to rehydrate the starchto any desired moisture content. The starch will preferably beneutralized to a pH of about 6 to 8 and rehydrated to a moisture contentabout 10 to about 13 percent.

DESCRIPTION OF TYPICAL DRY THINNING PROCESS

The dry thinning process of the invention will be further described inreference to a typical processing scheme such as shown in FIG. 1. Thereaction variables used in such a typical process will be as describedabove.

Dried starch, typically provided directly from a flash dryer as is knownin the art is provided through line 100 to a surge bin 101. The use of avessel such as the surge bin is desired to facilitate the feed of thestarch to the mass flow bins in a constant and continuous manner. Thecontent of the starch in the surge bin can be monitored convenientlythrough standard techniques such as the load cells 103. A constanttemperature should be maintained throughout the mass flow bin. It may benecessary to jacket or insulate the bin to maintain the temperature. Thestarch from the feed bin passes through a valve 105 and through anin-line weight indicator 107 and through another valve 105 intopneumatic feed line 111. Heated air is provided into pneumatic feed lineupstream from the starch entry point. Also, upstream from the starchentry point into the pneumatic feed line the hydrolyzing chemical, isfed into the heated air stream from hydrolyzing chemical storage tank113 through line 115.

The starch hydrolyzing chemical mixture is fed from the pneumaticconveying line 111 to two mass flow bins 123. This feed is controlled byvalves 117 and would typically be passed through dust collectors 121 asis known in the art. Heated air is provided to the head space of themass flow bins from the space air heater 133 through the airline 135. Aswith the surge bin, the contents of the mass flow bins can be monitoredthrough load cells 103.

The starch hydrolyzing chemical mixture then passes through the massflow bins under a plug flow regime as described above. The dry thinnedstarch passes from the mass flow bins and into the pneumatic conveyingline 125 wherein aqueous base is added through valve and line 127 toneutralize the starch hydrolyzing chemical mixture and water is addedthrough valve 129 to rehydrate the mixture. From line 119, the drythinned starch is then moved to conventional storage and packagingfacilities. Any hydrolyzing chemical such as HCl present in the airstream and in the head space of the reactors is vented through scrubber131.

APPLICATIONS IN THE PAPER INDUSTRY

The starch products of the invention can be utilized for the sizing andcoating of paper prepared from all types of both cellulosic andcombinations of cellulosic with non-cellulosic fibers. In addition,synthetic cellulose fibers of the viscous rayon or regenerated cellulosetype can also be used as well as recycled waste papers from varioussources.

All types of paper dyes and tints, pigments and fillers may be added tothe starch compositions (in the usual manner). Such materials includeclay, talc, titanium dioxide, calcium carbonate, calcium sulfate, anddiatomaceous earths. Other surface sizing compounds as well as pigments,dyes and lubricants can also be used in conjunction with the size andcoating compositions.

Application of non-pigmented starch compositions to paper at the sizepress is referred to as surface sizing. Application of size can also bemade at the calendar stack. Dry thinned starches of this invention canbe used in surface sizing applications for uncoated paper products byapplying the thinned starch to a paper sheet surface. A continuous filmof the starch composition is applied to both sides of the paper.Application of pigmented starch composition is referred to as colorcoating.

Surface sizing improves surface finish, produces a better printingsurface and improves the strength characteristics of the paper as wellas other properties. By proper control of viscosity, starch sizes can bedeposited primarily on the surface of the sheet or permitted topenetrated more deeply into the sheet to produce products with thedesired physical properties.

Paper coating refers to the application of a layer of pigment, adhesiveand other supplementary materials to the surface of dry paper or paperboard. Prior to coating the paper surface maybe sized with dry thinnedstarch. The composition, commonly referred to as a coating color, isapplied to the paper surface in the form of an aqueous suspension.Typical coating compositions contain pigment as the primary coatingmaterial and a starch adhesive to bond the pigment particles to eachother and to the paper. The most commonly used pigments are clay,calcium carbonate, titanium dioxide and combinations thereof. Othermaterials such as calcium sulfoaluminate, zinc sulfide, barium sulfate,calcium sulfate, calcium sulfite and diatomaceous silica pigments arealso used. Other additives, such as polymeric latexes may beincorporated. Such coatings may be applied to the paper during the papermaking process. Typically, however, coatings are applied as a separatestep. In either case, the process differs only in the auxiliaryequipment needed to perform the coating operation.

Paper or paper board is coated to produce a surface adequate forprinting processes. Coatings provide whiteness, brightness, gloss andopacity to paper along with a smoother more uniform surface. Differentprinting processes require different sheet properties and surfaceproperties. Formulations of coating compositions for such printingprocesses are well known.

The starch adhesive component of coating compositions must not only actas a binder for the pigment but also must act as a carrier, impactdesirable flow characteristics and leveling, regulate the degree ofwater retention of the coating composition and produce the desiredstrength, ink receptivity and ink holdout for optimum printingcharacteristics. The starch adhesive should be easy to prepare, have ahigh adhesive strength and have a stable viscosity during storage.Starch products of the instant invention satisfy these requirements.

Examples of two starch base coating formulation are given below:

EXAMPLE 1--LOW-GRADE PAPER COATING

50 parts # 1 clay

50 parts delaminated clay

10 parts styrene butadiene latex (SBR)

8 parts dry thinned waxy maize starch

0.5 parts insolubilizer

0.3 parts CMC (carboxy methyl cellulose)

1 part calcium stearate

The coating can be applied to paper to achieve a coat weight of 8 g/m²/side

EXAMPLE 2--MEDIUM GRADE PAPER COATING

85 parts #2 clay

15 parts calcium carbonate

10 parts SBR latex

6 parts dry thinned waxy maize starch

1 part calcium stearate

0.3 parts alginate

0.5 parts insolubilizer

This coating can be applied to paper to achieve a coat weight of 8 g/m²/side

The preceding description of specific embodiments for the presentinvention is not intended to be a complete list of every embodiment ofthe invention. Persons who are skilled in this field will recognize thatmodifications can be made to the specific embodiments described herethat would be within the scope of the present invention.

What is claimed:
 1. A thinned starch produced by a processcomprisingcontinuously feeding a mixture of a base starch and ahydrolyzing chemical to a plug flow reactor, said starch having amoisture content of between about 5% and about 17% by weight, saidhydrolyzing chemical being injected into said starch in an amountranging from about 0.04 to about 2.0% by weight dry solids basis;maintaining said mixture at a temperature of about 70° F. (21° C.) toabout 170° F. (77° C.); adjusting the feed to said plug flow reactor soas to attain plug flow conditions and to maintain a residence time ofthe mixture in the reactor from about 0.5 to about 6 hours; recoveringthe thinned starch; and neutralizing the mixture.
 2. The dry thinnedstarch of claim 1 wherein said base starch is a waxy maize starch. 3.The dry thinned starch of claim 1 wherein said base starch is dent cornstarch.
 4. The dry thinned starch of claim 3 wherein said base starch isa chemically modified dent corn starch.
 5. The dry thinned starch ofclaim 4 wherein said base starch is an hydroxyethylated dent cornstarch.
 6. A process for producing a dry thinned starchcomprisingcontinuously feeding a mixture of a base starch and ahydrolyzing chemical to a plug flow reactor, said starch having amoisture content of between about 5% and about 17% by weight, saidhydrolyzing chemical being injected into said starch in an amountranging from about 0.04 to about 2.0% by weight dry solids basis;maintaining said mixture at a temperature of about 70° F. (21° C.) toabout 170° F. (77° C.); adjusting the feed to said plug flow reactor soas to attain plug flow conditions and to maintain a residence time ofthe mixture in the reactor from about 0.5 to about 6 hours; recoveringthe thinned starch; and neutralizing the mixture.
 7. The process ofclaim 6 wherein said base starch is a waxy maize starch.
 8. The processof claim 6 wherein said base starch is dent corn starch.
 9. The processof claim 8 wherein said base starch is a chemically modified dent cornstarch.
 10. A process of claim 9, wherein said base starch is anhydroxyethylated dent corn starch.
 11. A thinned starch produced by aprocess comprisingcontinuously feeding a mixture of waxy maize starchand a hydrolyzing chemical to a plug flow reactor, said starch having amoisture content of between about 5% and about 17% by weight, saidhydrolyzing chemical being injected into said starch in an amountranging from about 0.04 to about 2.0% by weight dry solids basis;maintaining said mixture at a temperature of about 70° F. (21° C.) toabout 170° F. (77° C.); adjusting the feed to said plug flow reactor soas to attain plug flow conditions and to maintain a residence time ofthe mixture in the reactor from about 0.5 to about 6 hours; recoveringthe thinned starch; and neutralizing the mixture.
 12. A thinned starchproduced by a process comprisingcontinuously feeding a mixture of anhydroxyethylated starch and a hydrolyzing chemical to a plug flowreactor, said starch having a moisture content of between about 5% andabout 17% by weight, said hydrolyzing chemical being injected into saidstarch in an amount ranging from about 0.04 to about 2.0% by weight drysolids basis; maintaining said mixture at a temperature of about 70° F.(21° C.) to about 170° F. (77° C.); adjusting the feed to said plug flowreactor so as to attain plug flow conditions and to maintain a residencetime of the mixture in the reactor from about 0.5 to about 6 hours;recovering the thinned starch; and neutralizing the mixture.
 13. Aprocess for producing a dry thinned starch comprisingcontinuouslyfeeding a mixture of a waxy maize starch and a hydrolyzing chemical to aplug flow reactor, said starch having a moisture content of betweenabout 5% and about 17% by weight, said hydrolyzing chemical beinginjected into said starch in an amount ranging from about 0.04 to about2.0% by weight dry solids basis; maintaining said mixture at atemperature of about 70° F. (21° C.) to about 170° F. (77° C.);adjusting the feed to said plug flow reactor so as to attain plug flowconditions and to maintain a residence time of the mixture in thereactor from about 0.5 to about 6 hours; recovering the thinned starch;and neutralizing the mixture.
 14. A process for producing a dry thinnedstarch comprisingcontinuously feeding a mixture of a hydroxyethylatedstarch and a hydrolyzing chemical to a plug flow reactor, said starchhaving a moisture content of between about 5% and about 17% by weight,said hydrolyzing chemical being injected into said starch in an amountranging from about 0.04 to about 2.0% by weight dry solids basis;maintaining said mixture at a temperature of about 70° F. (21° C.) toabout 170° F. (77° C.); adjusting the feed to said plug flow reactor soas to attain plug flow conditions and to maintain a residence time ofthe mixture in the reactor from about 0.5 to about 6 hours; recoveringthe thinned starch; and neutralizing the mixture.
 15. A thinned starchproduced by a process comprisingcontinuously feeding a mixture of a basestarch and a hydrolyzing chemical selected from the group comprisinghydrogen chloride gas, HCl and sulfuric acid to a plug flow reactor,said starch having a moisture content of between about 5% and about 17%by weight, said hydrolyzing chemical being injected into said starch inan amount ranging from about 0.04 to about 0.5% by weight dry solidsbasis; maintaining said mixture at a temperature of about 70° F. (21°C.) to about 170° F. (77° C.); adjusting the feed to said plug flowreactor so as to attain plug flow conditions and to maintain a residencetime of the mixture in the reactor from about 0.5 to about 6 hours;recovering the thinned starch; and neutralizing the mixture.
 16. The drythinned starch of claim 15 wherein said base starch is a waxy maizestarch.
 17. The dry thinned starch of claim 15 wherein said base starchis dent corn starch.
 18. The dry thinned starch of claim 17 wherein saidbase starch is a chemically modified dent corn starch.
 19. The drythinned starch of claim 18 wherein said base starch is anhydroxyethylated dent corn starch.
 20. A process for producing a drythinned starch comprisingcontinuously feeding a mixture of a base starchand a hydrolyzing chemical selected from the group comprising hydrogenchloride gas, HCl and sulfuric acid to a plug flow reactor, said starchhaving a moisture content of between about 5% and about 17% by weight,said hydrolyzing chemical being injected into said starch in an amountranging from about 0.04 to about 0.5% by weight dry solids basis;maintaining said mixture at a temperature of about 70° F. (21° C.) toabout 170° F. (77° C.); adjusting the feed to said plug flow reactor soas to attain plug flow conditions and to maintain a residence time ofthe mixture in the reactor from about 0.5 to about 6 hours; recoveringthe thinned starch; and neutralizing the mixture.
 21. The process ofclaim 20 wherein said base starch is a waxy maize starch.
 22. Theprocess of claim 20 wherein said base starch is dent corn starch. 23.The process of claim 22 wherein said base starch is a chemicallymodified dent corn starch.
 24. A process of claim 23 wherein said basestarch is an hydroxyethylated dent corn starch.
 25. A thinned starchproduced by a process comprisingcontinuously feeding a mixture of a waxymaize starch and a hydrolyzing chemical selected from the groupcomprising hydrogen chloride gas, HCl and sulfuric acid to a plug flowreactor, said, starch having a moisture content of between about 5% andabout 17% by weight, said hydrolyzing chemical being injected into saidstarch in an amount ranging from about 0.04 to about 0.5% by weight drysolids basis; maintaining said mixture at a temperature of about 70° F.(21° C.) to about 170° F. (77° C.); adjusting the feed to said plug flowreactor so as to attain plug flow conditions and to maintain a residencetime of the mixture in the reactor from about 0.5 to about 6 hours;recovering the thinned starch; and neutralizing the mixture.
 26. Athinned starch produced by a process comprisingcontinuously feeding amixture of an hydroxyethylated starch and a hydrolyzing chemicalselected from the group comprising hydrogen chloride gas, HCl andsulfuric acid to a plug flow reactor, said starch having a moisturecontent of between about 5% and about 17% by weight, said hydrolyzingchemical being injected into said starch in an amount ranging from about0.04 to about 0.5% by weight dry solids basis; maintaining said mixtureat a temperature of about 70° F. (21° C.) to about 170° F. (77° C.);adjusting the feed to said plug flow reactor so as to attain plug flowconditions and to maintain a residence time of the mixture in thereactor from about 0.5 to about 6 hours; recovering the thinned starch;and neutralizing the mixture.
 27. A process for producing a dry thinnedstarch comprisingcontinuously feeding a mixture of a waxy maize starchand a hydrolyzing chemical selected from the group comprising hydrogenchloride gas, HCl and sulfuric acid to a plug flow reactor, said starchhaving a moisture content of between about 5% and about 17% by weight,said HCl being injected into said starch in an amount ranging from about0.04 to about 0.5% by weight dry solids basis; maintaining said mixtureat a temperature of about 70° F. (21° C.) to about 170° F. (77° C.);adjusting the feed to said plug flow reactor so as to attain plug flowconditions and to maintain a residence time of the mixture in thereactor from about 0.5 to about 6 hours; recovering the thinned starch;and neutralizing the mixture.
 28. A process for producing a dry thinnedstarch comprisingcontinuously feeding a mixture of a hydroxyethylatedstarch and a hydrolyzing chemical selected from the group comprisinghydrogen chloride gas, HCl and sulfuric acid to a plug flow reactor,said starch having a moisture content of between about 5% and about 17%by weight, said HCl being injected into said starch in an amount rangingfrom about 0.04 to about 0.5% by weight dry solids basis; maintainingsaid mixture at a temperature of about 70° F. (21° C.) to about 170° F.(77° C.); adjusting the feed to said plug flow reactor so as to attainplug flow conditions and to maintain a residence time of the mixture inthe reactor from about 0.5 to about 6 hours; recovering the thinnedstarch; and neutralizing the mixture.
 29. A thinned starch produced by aprocess comprisingcontinuously feeding a mixture of a base starch andHCl to a plug flow reactor, said starch having a moisture content ofbetween about 5% and about 17% by weight, said HCl being injected intosaid starch in an amount ranging from about 0.04 to about 0.5% by weightdry solids basis; maintaining said mixture at a temperature of about 70°F. (21° C.) to about 170° F. (77° C.); adjusting the feed to said plugflow reactor so as to attain plug flow conditions and to maintain aresidence time of the mixture in the reactor from about 0.5 to about 6hours; recovering the thinned starch; and neutralizing the mixture. 30.The dry thinned starch of claim 29 wherein said base starch is a waxymaize starch.
 31. The dry thinned starch of claim 29 wherein said basestarch is dent corn starch.
 32. The dry thinned starch of claim 31wherein said base starch is a chemically modified dent corn starch. 33.The dry thinned starch of claim 32 wherein said base starch is anhydroxyethylated dent corn starch.
 34. A process for producing a drythinned starch comprisingcontinuously feeding a mixture of a base starchand HCl to a plug flow reactor, said starch having a moisture content ofbetween about 5% and about 17% by weight, said HCl being injected intosaid starch in an amount ranging from about 0.04 to about 0.5% by weightdry solids basis; maintaining said mixture at a temperature of about 70°F. (21° C.) to about 170° F. (77° C.); adjusting the feed to said plugflow reactor so as to maintain a residence time of the mixture in thereactor from about 0.5 to about 6 hours; recovering the thinned starch;and neutralizing the mixture.
 35. The process of claim 34 wherein saidbase starch is a waxy maize starch.
 36. The process of claim 34 whereinsaid base starch is dent corn starch.
 37. The process of claim 36wherein said base starch is a chemically modified dent corn starch. 38.A process of claim 37 wherein said base starch is an hydroxyethylateddent corn starch.
 39. A thinned starch produced by a processcomprisingcontinuously feeding a mixture of waxy maize starch and HCl toa plug flow reactor, said starch having a moisture content of betweenabout 5% and about 17% by weight, said HCl being injected into saidstarch in an amount ranging from about 0.04 to about 0.5% by weight drysolids basis; maintaining said mixture at a temperature of about 70° F.(21° C.) to about 170° F. (77° C.); adjusting the feed to said plug flowreactor so as to attain plug flow conditions and to maintain a residencetime of the mixture in the reactor from about 0.5 to about 6 hours;recovering the thinned starch; and neutralizing the mixture.
 40. Athinned starch produced by a process comprisingcontinuously feeding amixture of an hydroxyethylated starch and HCl to a plug flow reactor,said starch having a moisture content of between about 5% and about 17%by weight, said HCl being injected into said starch in an amount rangingfrom about 0.04 to about 0.5% by weight dry solids basis; maintainingsaid mixture at a temperature of about 70° F. (21° C.) to about 170° F.(77° C.); adjusting the feed to said plug flow reactor so as to attainplug flow conditions and to maintain a residence time of the mixture inthe reactor from about 0.5 to about 6 hours; recovering the thinnedstarch; and neutralizing the mixture.
 41. A process for producing a drythinned starch comprisingcontinuously feeding a mixture of a waxy maizestarch and HCl to a plug flow reactor, said starch having a moisturecontent of between about 5% and about 17% by weight, said HCl beinginjected into said starch in an amount ranging from about 0.04 to about0.5% by weight dry solids basis; maintaining said mixture at atemperature of about 70° F. (21° C.) to about 170° F. (77° C.);adjusting the feed to said plug flow reactor so as to attain plug flowconditions and to maintain a residence time of the mixture in thereactor from about 0.5 to about 6 hours; recovering the thinned starch;and neutralizing the mixture.
 42. A process for producing a dry thinnedstarch comprisingcontinuously feeding a mixture of a hydroxyethylatedstarch and HCl to a plug flow reactor, said starch having a moisturecontent of between about 5% and about 17% by weight, said HCl beinginjected into said starch in an amount ranging from about 0.04 to about0.5% by weight dry solids basis; maintaining said mixture at atemperature of about 70° F. (21° C.) to about 170° F. (77° C.);adjusting the feed to said plug flow reactor so as to attain plug flowconditions and to maintain a residence time of the mixture in thereactor from about 0.5 to about 6 hours; recovering the thinned starch;and neutralizing the mixture.